The overall goal of this project is to determine the mechanisms responsible for the reduction in coronary vascular nitric oxide synthesis which occurs during the development of heart failure. Furthermore, we will determine the implications of the loss of NO production to the regulation of both vascular resistance and oxygen consumption in the heart. To insure that these results apply to human disease states and that they are applicable to diseases which result in heart failure, we will study human coronary microvessels and dogs with an aortic stenosis as well as a dilated myopathy caused by rapid pacing. Finally pharmacologic and molecular biology techniques will be used to determine the altered mechanisms involved in the reduced production of NO. We will determine the impact of altered NO production on the control of myocardial oxygen consumption in vivo and in vitro and will extend our studies of coronary microvessel NO production to microvessels isolated from the failing explanted human heart. An important control mechanism governing the production of NO in coronary microvessels is the local formation of kinins. This will receive emphasis in our studies in vitro since ACE inhibitors inhibit kinin breakdown and are used clinically in the treatment of heart failure. In collaboration with Dr. Wolin (Project 1) we will investigate altered mitochondrial function, with Dr. Kaley (Project 4) altered flow dependent regulation of microvessels in vitro; and with Dr. Anversa (Project 3) the role of NO as a signal involved in cardiac remodeling. Dr. Sessa will participate in order to extend our previous studies of alterations of endothelial NOS gene expression from large vessel endothelium to microvessel endothelium since this is the vessel which controls resistance and blood flow in the heart. We will measure nitrite and nitrate in aqueous solution or plasma as a service to all the program project components. Our studies will address the role of reduced NO production in the coronary circulation in the genesis of heart failure in well controlled animal models and also in the human heart.